As leading shares fell for the ninth day running, Heritage Oil lost nearly 6% after a tribunal in Uganda ruled it was liable for a $404m tax bill relating to the $1.45bn sale of its assets in the country to Tullow Oil last year.

The company - run by former mercenary Tony Buckingham - said it would appeal the ruling, and has already started arbitration proceedings in London since it maintains the deal was not subject to capital gains tax since it was implemented outside Uganda. Analysts said the Ugandan tribunal judgement had been expected. Oriel Securities said:

Overall this comes as no surprise. In total the disputed tax amount could be worth 90p a share net to Heritage. However timing on the arbitration remains unclear.

Heritage dropped 9.6p to 160.4p.

Meanwhile the FTSE 100 ended 12.21 points lower at 5127.57, its worse run of losses since January 2003 when it fell 11 trading days in a row. It means around £107bn has been wiped off the value of Britain's top companies during the losing streak. With no guidance from Wall Street, closed for the Thanksgiving holiday, investors concentrated on the latest developments in the eurozone debt crisis. News that Fitch had downgraded Portugal unsettled the markets, but the main negative was the lack of any new plans to deal with the crisis following a meeting in Strasbourg between Nicolas Sarkozy, Angela Merkel and Mario Monti.

The falls were across the board, with Shire down 48p at £19.62 and Inmarsat - in danger of losing its place in the leading index at the forthcoming review - 7.8p lower at 389.3p.

BAE Systems fell 5.2p to 251.4p. As the government announced the sale of 72 retired Harrier aircraft to the US for spare parts, the company was criticised in parliament for its plans to cut nearly 3,000 UK jobs.

Banks recovered some of their recent losses, with Royal Bank of Scotland rising 0.63p to 17.97p and Barclays 4.6p better at 152.5p.

Among the mid-caps Dixons Retail rose 0.66p to 10.02p after its half year loss of £25.3m was slightly better than analysts had feared, while Mothercare added 19.5p to 149.6p on vague bid talk.

Takeover speculation also lifted Cable & Wireless Worldwide, whose shares have slumped since its recent poor results but climbed 0.7p to 14.9p. Analyst Mark James at Liberum Capital said the company's lowly rating could attract bidders such as mobile operators like Vodafone or O2. Moving his recommendation from sell to buy, he has put a 20p target on CWW and said:

Whilst it's hard to see sentiment [towards the company] improving any time, we do feel however that the current price will encourage the resurrection of bid speculation.
For our part, whilst we continue to believe the CWW assets are particularly unattractive, at these levels there may be others who could benefit more from them than existing shareholders. An example would be the UK based mobile operators. Whilst CWW is struggling to make a decent return in its own right (high fixed network costs, and insufficient revenues to drive margins to those enjoyed by incumbent telcos), others could potentially make more use of its infrastructure. The UK operations of Vodafone, say, or Telefonica's O2, both make earnings before interest and tax of around £700m a year, could use presumably use the CWW tax losses and also benefit from its network infrastructure. As an indication, carrier revenues at CWW run at some £300m a year, around half of the £600m enterprise value.

Enterprise Inns added 3.25p to 33.5p after the government decided against imposing a statutory code of practice for the industry, instead sticking with self regulation. Enterprise chief executive Ted Tuppen said:

We are delighted the government has concluded that self-regulation in the UK pub industry can provide effective protection for individual publicans, and that the entire industry may now concentrate all of its energy and resources on the real challenges facing UK pubs without further distraction.

But rival Punch Taverns, where investors are focussed more on its debt levels, was unchanged at 11.5p.

Lower down the market Gulf Keystone Petroleum, which has operations in Kurdistan, jumped 21.75p to 168.5p with 12m shares traded on speculative talk of a possible 300p a share offer from Exxon Mobil, which is attempting to set up in the region. Traders were wary of the tale, however.

Finally, Aim-listed drug discovery company Summit closed 0.25p higher at 6p after the US Food & Drug Administration granted orphan drug status to its SMT C1100 treatment for Duchenne Muscular Dystrophy, a fatal genetic neuromuscular disorder for which there is currently no cure. The orphan drug status grants Summit, among other benefits, a seven year period of market exclusivity in the US.